Since machining hard, abrasion, erosion and/or wear resistant materials is generally both difficult and expensive, it is common practice to form a metal part with a desired configuration and subsequently treat one or more portions of the metal part to provide desired abrasion, erosion and/or wear resistance. Examples may include directly hardening such surfaces (carburizing and/or nitriding) one or more surfaces of a metal part or applying a layer of hard, abrasion, erosion and/or wear resistant material (hardfacing) to one or more surfaces of a metal part depending upon desired amounts of abrasion, erosion and/or wear resistance for such surfaces. For applications when resistance to extreme abrasion, erosion and/or wear of a working surface and/or associated substrate is desired, a layer of hard, abrasion, erosion and/or wear resistant material (hardfacing) formed in accordance with the present disclosure may be applied to the working surface to protect the associated substrate.
Hardfacing may be generally defined as a layer of hard, abrasion resistant material applied to a less resistant surface or substrate by plating, welding, spraying or other well known deposition techniques. Hardfacing is frequently used to extend the service life of drill bits and other downhole tools used in the oil and gas industry. Tungsten carbide and various alloys of tungsten carbide are examples of hardfacing materials widely used to protect drill bits and other downhole tools associated with drilling and producing oil and gas wells.
Hardfacing is typically a mixture of a hard, wear-resistant material embedded in a matrix deposit which may be fused with a surface of a substrate by forming metallurgical type bonds to ensure uniform adherence of the hardfacing with the substrate. For some applications, wear resistant material such as an alloy of tungsten carbide and/or cobalt may be placed in a steel tube which serves as a welding rod during welding of hardfacing with a substrate. This technique of applying hardfacing may sometimes referred to as “tube rod welding.” Tungsten carbide/cobalt hardfacing applied with tube rods has been highly successful in extending the service life of drill bits and other downhole tools.
A wide variety of hardfacing materials have been satisfactorily used on drill bits and other downhole tools. Frequently used hardfacing materials include sintered tungsten carbide particles in a steel alloy matrix deposit. Tungsten carbide particles may include grains of monotungsten carbide, ditungsten carbide and/or macrocrystalline tungsten carbide. Prior tungsten carbide particles have typically been formed with no binding material (0% by weight of binding material) or with relative high percentages (5% or greater) by weight of binding material in such tungsten carbide particles. Spherical cast tungsten carbide may typically be formed with no binding material. Examples of binding materials used to form tungsten carbide particles may include, but are not limited to, cobalt, nickel, boron, molybdenum, niobium, chromium, iron and alloys of these elements.
For some applications loose hardfacing materials may be placed in a hollow tube or welding rod and applied to a substrate using conventional welding techniques. As a result of the welding process, a matrix deposit including both metal alloys from melting associated surface portions of the substrate and from melting metal alloys associated with the welding rod or hollow tube may bond with the hardfacing materials. Various alloys of cobalt, nickel, copper and/or iron may form portions of the matrix deposit. Other heavy metal carbides and nitrides, in addition to tungsten carbide, have been used to form hardfacing.